Galileo Galilei was born on February 15, 1564 in Pisa, Italy. Galileo pioneered "experimental scientific method," and was the first to use a refracting telescope to make important astronomical discoveries.In 1604 Galileo learned of the invention of the telescope in Holland. From the barest description he constructed a vastly superior model. With it he made a series of profound discoveries, including the moons of planet Jupiter and the phases of the planet Venus (similar to those of Earth's moon).
As a professor of astronomy at University of Pisa, Galileo was required to teach the accepted theory of his time that the sun and all the planets revolved around the Earth. Later at University of Padua he was exposed to a new theory, proposed by Nicolaus Copernicus, that the Earth and all the other planets revolved around the sun. Galileo's observations with his new telescope convinced him of the truth of Copernicus's sun-centered or heliocentric theory
Galileo's support for the heliocentric theory got him into trouble with the Roman Catholic Church. In 1633 the Inquisition convicted him of heresy and forced him to recant (publicly withdraw) his support of Copernicus. They sentenced him to life imprisonment, but because of his advanced age allowed him serve his term under house arrest at his villa outside of Florence, Italy.
Galileo's originality as a scientist lay in his method of inquiry. First he reduced problems to a simple set of terms on the basis of everyday experience and common-sense logic. Then he analyzed and resolved them according to simple mathematical descriptions. The success with which he applied this technique to the analysis of motion opened the way for modern mathematical and experimental physics. Isaac Newton used one of Galileo's mathematical descriptions, "The Law of Inertia," as the foundation for his "First Law of Motion." Galileo died in 1642, the year of Newton's birth.